Java tutorial
/* * The Apache Software License, Version 1.1 * * Copyright (c) 1999,2004 The Apache Software Foundation. All rights * reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in * the documentation and/or other materials provided with the * distribution. * * 3. 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For more * information on the Apache Software Foundation, please see * <http://www.apache.org/>. * */ package org.apache.jasper.compiler; import java.io.InputStream; import java.net.JarURLConnection; import java.net.URL; import java.net.URLClassLoader; import java.net.URLConnection; import java.util.Enumeration; import java.util.Hashtable; import java.util.Iterator; import java.util.Set; import java.util.jar.JarEntry; import java.util.jar.JarFile; import javax.servlet.ServletContext; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; import org.apache.jasper.JasperException; import org.apache.jasper.xmlparser.ParserUtils; import org.apache.jasper.xmlparser.TreeNode; /** * A container for all tag libraries that are defined "globally" * for the web application. * * Tag Libraries can be defined globally in one of two ways: * 1. Via <taglib> elements in web.xml: * the uri and location of the tag-library are specified in * the <taglib> element. * 2. Via packaged jar files that contain .tld files * within the META-INF directory, or some subdirectory * of it. The taglib is 'global' if it has the <uri> * element defined. * * A mapping between the taglib URI and its associated TaglibraryInfoImpl * is maintained in this container. * Actually, that's what we'd like to do. However, because of the * way the classes TagLibraryInfo and TagInfo have been defined, * it is not currently possible to share an instance of TagLibraryInfo * across page invocations. A bug has been submitted to the spec lead. * In the mean time, all we do is save the 'location' where the * TLD associated with a taglib URI can be found. * * When a JSP page has a taglib directive, the mappings in this container * are first searched (see method getLocation()). * If a mapping is found, then the location of the TLD is returned. * If no mapping is found, then the uri specified * in the taglib directive is to be interpreted as the location for * the TLD of this tag library. * * @author Pierre Delisle * @author Jan Luehe */ public class TldLocationsCache { // Logger private static Log log = LogFactory.getLog(TldLocationsCache.class); /** * The types of URI one may specify for a tag library */ public static final int ABS_URI = 0; public static final int ROOT_REL_URI = 1; public static final int NOROOT_REL_URI = 2; private static final String WEB_XML = "/WEB-INF/web.xml"; private static final String FILE_PROTOCOL = "file:"; private static final String JAR_FILE_SUFFIX = ".jar"; /** * The mapping of the 'global' tag library URI to the location (resource * path) of the TLD associated with that tag library. The location is * returned as a String array: * [0] The location * [1] If the location is a jar file, this is the location of the tld. */ private Hashtable mappings; private boolean initialized; private ServletContext ctxt; private boolean redeployMode; //********************************************************************* // Constructor and Initilizations public TldLocationsCache(ServletContext ctxt) { this(ctxt, true); } /** Constructor. * * @param ctxt the servlet context of the web application in which Jasper * is running * @param redeployMode if true, then the compiler will allow redeploying * a tag library from the same jar, at the expense of slowing down the * server a bit. Note that this may only work on JDK 1.3.1_01a and later, * because of JDK bug 4211817 fixed in this release. * If redeployMode is false, a faster but less capable mode will be used. */ public TldLocationsCache(ServletContext ctxt, boolean redeployMode) { this.ctxt = ctxt; this.redeployMode = redeployMode; mappings = new Hashtable(); initialized = false; } /** * Gets the 'location' of the TLD associated with the given taglib 'uri'. * * Returns null if the uri is not associated with any tag library 'exposed' * in the web application. A tag library is 'exposed' either explicitly in * web.xml or implicitly via the uri tag in the TLD of a taglib deployed * in a jar file (WEB-INF/lib). * * @param uri The taglib uri * * @return An array of two Strings: The first element denotes the real * path to the TLD. If the path to the TLD points to a jar file, then the * second element denotes the name of the TLD entry in the jar file. * Returns null if the uri is not associated with any tag library 'exposed' * in the web application. */ public String[] getLocation(String uri) throws JasperException { if (!initialized) { init(); } return (String[]) mappings.get(uri); } /** * Returns the type of a URI: * ABS_URI * ROOT_REL_URI * NOROOT_REL_URI */ public static int uriType(String uri) { if (uri.indexOf(':') != -1) { return ABS_URI; } else if (uri.startsWith("/")) { return ROOT_REL_URI; } else { return NOROOT_REL_URI; } } private void init() throws JasperException { if (initialized) return; try { processWebDotXml(); scanJars(); processTldsInFileSystem("/WEB-INF/"); initialized = true; } catch (Exception ex) { throw new JasperException(Localizer.getMessage("jsp.error.internal.tldinit", ex.getMessage())); } } /* * Populates taglib map described in web.xml. */ private void processWebDotXml() throws Exception { // Acquire an input stream to the web application deployment descriptor InputStream is = ctxt.getResourceAsStream(WEB_XML); if (is == null) { if (log.isWarnEnabled()) { log.warn(Localizer.getMessage("jsp.error.internal.filenotfound", WEB_XML)); } return; } // Parse the web application deployment descriptor TreeNode webtld = new ParserUtils().parseXMLDocument(WEB_XML, is); // Allow taglib to be an element of the root or jsp-config (JSP2.0) TreeNode jspConfig = webtld.findChild("jsp-config"); if (jspConfig != null) { webtld = jspConfig; } Iterator taglibs = webtld.findChildren("taglib"); while (taglibs.hasNext()) { // Parse the next <taglib> element TreeNode taglib = (TreeNode) taglibs.next(); String tagUri = null; String tagLoc = null; TreeNode child = taglib.findChild("taglib-uri"); if (child != null) tagUri = child.getBody(); child = taglib.findChild("taglib-location"); if (child != null) tagLoc = child.getBody(); // Save this location if appropriate if (tagLoc == null) continue; if (uriType(tagLoc) == NOROOT_REL_URI) tagLoc = "/WEB-INF/" + tagLoc; String tagLoc2 = null; if (tagLoc.endsWith(JAR_FILE_SUFFIX)) { tagLoc = ctxt.getResource(tagLoc).toString(); tagLoc2 = "META-INF/taglib.tld"; } mappings.put(tagUri, new String[] { tagLoc, tagLoc2 }); } } /** * Scans the given JarURLConnection for TLD files located in META-INF * (or a subdirectory of it), adding an implicit map entry to the taglib * map for any TLD that has a <uri> element. * * @param conn The JarURLConnection to the JAR file to scan * @param ignore true if any exceptions raised when processing the given * JAR should be ignored, false otherwise */ private void scanJar(JarURLConnection conn, boolean ignore) throws JasperException { JarFile jarFile = null; String resourcePath = conn.getJarFileURL().toString(); try { if (redeployMode) { conn.setUseCaches(false); } jarFile = conn.getJarFile(); Enumeration entries = jarFile.entries(); while (entries.hasMoreElements()) { JarEntry entry = (JarEntry) entries.nextElement(); String name = entry.getName(); if (!name.startsWith("META-INF/")) continue; if (!name.endsWith(".tld")) continue; InputStream stream = jarFile.getInputStream(entry); try { String uri = getUriFromTld(resourcePath, stream); // Add implicit map entry only if its uri is not already // present in the map if (uri != null && mappings.get(uri) == null) { mappings.put(uri, new String[] { resourcePath, name }); } } finally { if (stream != null) { try { stream.close(); } catch (Throwable t) { // do nothing } } } } } catch (Exception ex) { if (!redeployMode) { // if not in redeploy mode, close the jar in case of an error if (jarFile != null) { try { jarFile.close(); } catch (Throwable t) { // ignore } } } if (!ignore) { throw new JasperException(ex); } } finally { if (redeployMode) { // if in redeploy mode, always close the jar if (jarFile != null) { try { jarFile.close(); } catch (Throwable t) { // ignore } } } } } /* * Searches the filesystem under /WEB-INF for any TLD files, and adds * an implicit map entry to the taglib map for any TLD that has a <uri> * element. */ private void processTldsInFileSystem(String startPath) throws Exception { Set dirList = ctxt.getResourcePaths(startPath); if (dirList != null) { Iterator it = dirList.iterator(); while (it.hasNext()) { String path = (String) it.next(); if (path.endsWith("/")) { processTldsInFileSystem(path); } if (!path.endsWith(".tld")) { continue; } InputStream stream = ctxt.getResourceAsStream(path); String uri = null; try { uri = getUriFromTld(path, stream); } finally { if (stream != null) { try { stream.close(); } catch (Throwable t) { // do nothing } } } // Add implicit map entry only if its uri is not already // present in the map if (uri != null && mappings.get(uri) == null) { mappings.put(uri, new String[] { path, null }); } } } } /* * Returns the value of the uri element of the given TLD, or null if the * given TLD does not contain any such element. */ private String getUriFromTld(String resourcePath, InputStream in) throws JasperException { // Parse the tag library descriptor at the specified resource path TreeNode tld = new ParserUtils().parseXMLDocument(resourcePath, in); TreeNode uri = tld.findChild("uri"); if (uri != null) { String body = uri.getBody(); if (body != null) return body; } return null; } /* * Scans all JARs accessible to the webapp's classloader and its * parent classloaders for TLDs. * * The list of JARs always includes the JARs under WEB-INF/lib, as well as * all shared JARs in the classloader delegation chain of the webapp's * classloader. * * The latter constitutes a Tomcat-specific extension to the TLD search * order defined in the JSP spec. It allows tag libraries packaged as JAR * files to be shared by web applications by simply dropping them in a * location that all web applications have access to (e.g., * <CATALINA_HOME>/common/lib). */ private void scanJars() throws Exception { ClassLoader loader = Thread.currentThread().getContextClassLoader(); while (loader != null) { if (loader instanceof URLClassLoader) { URL[] urls = ((URLClassLoader) loader).getURLs(); for (int i = 0; i < urls.length; i++) { URLConnection conn = urls[i].openConnection(); if (conn instanceof JarURLConnection) { scanJar((JarURLConnection) conn, true); } else { String urlStr = urls[i].toString(); if (urlStr.startsWith(FILE_PROTOCOL) && urlStr.endsWith(JAR_FILE_SUFFIX)) { URL jarURL = new URL("jar:" + urlStr + "!/"); scanJar((JarURLConnection) jarURL.openConnection(), true); } } } } loader = loader.getParent(); } } }